What’s the Difference Between Hallucinations, Delusions, and Illusions?
Dementia-related psychosis means seeing and hearing things that aren't really there. Learn more about these challenging symptoms.
It's disturbing to see your loved one talking to an empty chair, or telling you there's someone in your basement (when there's not). George Grossberg, M.D., professor and director of geriatric psychiatry at Saint Louis University School of Medicine in Missouri, explains the different ways dementia-related psychosis can interfere with a patient's perception of reality.
The notion of trying to differentiate among delusions, hallucinations, and illusions is important. A delusion that a person can have is any kind of firm, fixed, false belief that they have that just doesn't agree, doesn't concur, doesn't jive with our sense of reality. An example might be, my home is not my home, or the delusion might be that the food is poisoned, which we know it's not, but they feel it is. Or the delusion might be a more unusual one, but one that we do see, where they may say that their spouse is an impostor someone they've been married to for 56 years. I had a patient just like that recently, isn't really their husband or their wife. That's a delusion.
Hallucinations basically are sensory in nature and by far away the most common hallucinations are things that people see or hear or imagine that you and I don't hear or see or imagine, are visual hallucinations. They're seeing things. They're seeing this family in the basement that you and I don't see. They're seeing the snake crawling on the ground, that may be dangerous, that you and I don't see. Or they may be hearing things which is less common. There are even other unusual kind of hallucinatory, sensory experiences, things like olfactory, smelling, things that you and I don't smell. Having a sense of presence, that there's somebody around us looking over my shoulder, but then when you turn around, they're gone. They're not there. Now, these are the psychotic symptoms.
Illusions, basically, which are always visual, are sensory misinterpretations. They're not psychotic symptoms necessarily. In fact, they may even be due to something like having cataracts that need to be extracted or addressed. I'll give you a good example of it. I had a patient recently and this can occur even not in the context of dementia, but with dementia as well, who sleeps in a very fancy bed in her bedroom. She has these intricately carved bedposts, four of those. She was telling me that one morning as she woke up, she looked at one of these carved bedposts and it looked like it was a bunch of snakes. It didn't look like the bedpost, but that didn't last. Nonetheless, it kind of disturbed her for a moment. Then she was OK.
Illusions are really misinterpretations that are based on something that's in the environment that triggers it. We're a lot less concerned about those than we are about delusions and/or hallucinations. Of course, we need to make sure if they're visual, which the illusions are, that we address things like vision or visual impairment, make sure that they're not just happening during the dream state or as one awakes from the dream state, because those can be addressed. That's much less worrisome.